Greek authorities on Monday began transferring hundreds of refugees from the island of Lesbos to reduce chronic overcrowding that caused hardship and fanned tensions with locals.

Over 700 people were to sail to the Greek mainland aboard a ferry, organisers said, three weeks after a sprawling camp on the island burned down.

Another group will leave on Thursday, state agency ANA said.

Some 2,500 refugees and asylum seekers are to be relocated overall, following coronavirus tests, according to the migration ministry.

Over 12,000 asylum seekers were left homeless on September 8 after a fire ravaged the Lesbos camp of Moria, Europe’s largest.

Six Afghan youths are on trial for arson in connection to the fire. They deny the charges.

The Moria camp was notorious for overcrowding, poor sanitation and ethnic gang violence. The fire broke out shortly after more than 30 people there tested positive for coronavirus.

Also on Monday, Greek police said they had identified 33 aid workers who allegedly facilitated illegal migration to Lesbos.

A Greek police source later said the "preliminary” investigation was still under way.

A police statement said the suspects, who worked for four non-governmental organisations, were part of "an organised network” created to "systematically” facilitate illegal migration to the island.

Two other foreign nationals — identified by state TV ERT as an Afghan and an Iranian — were also part of the alleged operation, the police said.

No information was given on the aid groups in question, the identities of the suspects, or whether any were already in custody.

The police said the alleged operation was active from at least June, "providing substantial assistance to organised migrant-smuggling networks” in over more than cases by helping direct migrant boats to shore safely.

Meanwhile, Germany has offered to take 1,500 asylum seekers from Greece, including former Moria residents.

For its part, France has offered to take in 500 minors from the camp.

Authorities and local residents on Lesbos had long campaigned for the immediate removal of most of the asylum seekers.

After the camp burned down, a makeshift tent facility was hurriedly erected to house some 9,500 people.

But the temporary camp, on a hill overlooking the sea, is ill-equipped to handle winter conditions.

The government is now in talks to build a smaller permanent camp on the island.